1. Technical Field
The present disclosure generally relates to electrosurgery. More particularly, the present disclosure relates to electrosurgical systems and methods for monitoring power dosage of electrosurgical energy delivered to tissue.
2. Background of Related Art
Electrosurgery involves the application of high-frequency electric current to cut or modify biological tissue during an electrosurgical operation. Electrosurgery is performed using an electrosurgical generator, an active electrode, and a return electrode. The electrosurgical generator (also referred to as a power supply or waveform generator) generates an alternating current (AC), which is applied to a patient's tissue through the active electrode and is returned to the electrosurgical generator through the return electrode. The AC typically has a frequency above 100 kilohertz (kHz) to avoid muscle and/or nerve stimulation.
During electrosurgery, the AC generated by the electrosurgical generator is conducted through tissue disposed between the active and return electrodes. The electrical energy (also referred to as electrosurgical energy) delivered to the tissue is converted into heat due to the resistivity of the tissue, which causes the tissue temperature to rise. The electrosurgical generator monitors the dosage of power (i.e., electrical energy per time) to control the heating of the tissue. Although many other variables affect the total heating of the tissue, increased current density and resistance of the tissue usually lead to increased heating. The electrosurgical energy is typically used for cutting, dissecting, ablating, coagulating, and/or sealing tissue.
The two basic types of electrosurgery employed are monopolar and bipolar electrosurgery. Both of these types of electrosurgery use an active electrode and a return electrode. In bipolar electrosurgery, the surgical instrument includes an active electrode and a return electrode on the same instrument or in very close proximity to one another, which cause current to flow through a small amount of tissue. In monopolar electrosurgery, the return electrode is located elsewhere on the patient's body and is typically not a part of the electrosurgical instrument itself. In monopolar electrosurgery, the return electrode is part of a device typically referred to as a return pad.
An electrosurgical generator makes use of voltage and current sensors to measure quantities, such as power, for controlling the output of the electrosurgical generator to achieve a desired clinical effect. A cable, which may be more than a meter in length, connects the electrosurgical generator to the active and return electrodes and is used to deliver electrosurgical energy to tissue being treated. The cable creates a circuit network between the voltage and current sensors and the tissue being treated, which distorts the voltage and current waveforms generated by the electrosurgical generator so that the waveforms deviate from the desired pure sinusoidal, rectangular, sawtooth, pulse, triangular, or blended waveforms commonly used for electrosurgery. Thus, to more accurately monitor power, many generators employ compensation algorithms that account for the impedance of the circuit network of the cable.
These compensation algorithms typically involve complex computations, which may be computationally inefficient and expensive. As a result, the real-time embedded software systems that perform the complex computations introduce time delays into the control algorithms for controlling the electrosurgical generator. When these time delays are accumulated, the generator may under-deliver or over-deliver electrosurgical energy to the tissue being treated.